From USA Today (link):
For decades, political prisoners held by China have been on the agenda at U.S.-China summit meetings. U.S. presidents raise prominent prisoners’ cases and press for their release in the hope their Chinese counterparts will make a goodwill gesture.
Human rights activists say prisoner releases have declined since Hu became China’s leader in 2002. “We have not seen any inclination by the Hu administration to make any symbolic moves to appease human rights concerns,” says Nicholas Bequelin, a China expert with Human Rights Watch. “The fact that China refuses to do it is an indication of how conservative and how little inclined to liberalization this administration is.”